Nowadays, a laser sensor (or laser distance sensor) having information on angles and distances is being widely used as fields of robots, autonomous mobile vehicles, etc. are extended. In an industrial field or a military field, a camera image is being much used together with the laser sensor in order to utilize more information. However, in order to use the camera together with the laser sensor, a calibration for obtaining a relation between the laser sensor and the camera has to be performed.
As the conventional calibration method, has been mainly used a method for obtaining a relation between a camera image and a laser distance sensor by converting laser points of the laser distance sensor into laser points of a camera, and then by converting the corresponding points of the camera into laser points of a camera image (refer to FIG. 10). In order to estimate positions of the laser points of the camera image, a visible laser distance sensor has been used, or a camera image with respect to a checkboard and restriction conditions on positions of the camera and the laser distance sensor have been used. Alternatively, geometric characteristics of a checkboard have been used.
However, these methods may have the following problems. More concretely, in order to convert laser points into a camera image, an intrinsic parameter has to be firstly calculated. Then, an extrinsic parameter has to be calculated. Here, the extrinsic parameter indicates a rotation and a translation between a camera coordinates system and an image captured by a camera. Furthermore, the conversion matrix with respect to a coordinate system of the camera and a coordinate system of the laser sensor has to be calculated again. This may cause a calculation time and a complicated degree to be increased.